1. Field of the Invention
This invention relates to visual examination of the features of the human body such as the venous system and particularly to improvements in the method of gaining intravenous access by enhancing the view of the venous system by infrared illumination.
2. Prior Art and Information Disclosure
The difficulties of gaining intravenous access such as for drawing blood, intravenous fusion, etc., are well known to vary from one patient to another. Some patients have very prominent veins and this situation simplifies the procedure although, even for some of these patients, their veins have a tough resiliency that makes the veins difficult to penetrate with a hypodermic needle. In the context of this specification, the term, hypodermic needled, will be understood to mean any access device such as a syringe with needle for drawing blood, intravenous cathater, etc. In other patients, the veins are small, deepset, and scarcely visible so that gaining intravenous access is very unpleasant for both the practitioner and the patient. The complexion of the patient can be another troublesome factor. For example, the veins of Afro-Americans are not nearly as visible as the veins of many other patients which hinders the process of finding a vein and drawing blood therefrom. Infants have immature vacular development. Obese patients have venous structure that is difficult to penetrate. At the very least, these complications can greatly increase the stress experienced by the patient. At worst, delays in gaining intravenous access can result in death.
Numerous studies have been reported on the use of infrared illumination to noninvasively examine the venous system. These studies have been confined to the use of black and white infrared photography, defined as the technique of focussing an infrared image onto an emulsion.
Two approaches are used in black and white infrared photography.
In one approach, the subject producing the image reflects varying amounts of infra red radiation falling on it.
In another approach, the subject can emit luminescence in the infrared range when illuminated with visible light.
Noninvasive studies of the vascular system using infra red photography have resulted in some well known observations as discussed in the publication "Medical Infrared Photography" published by the Kodak Corp., Rochester, N.Y. which is hereby incorporated by reference into this specification.
In particular, it has been found that the actinic band of infrared has been the most useful for medical infrared photography. The actinic band lies in the range from 700 to 900 nanometers. This is the range of the near infra red. It has been found in studies using black and white infrared photography, that skin and superficial tissues reflect most of the radiation in this range of the spectrum while the blood absorbs much of this radiation. This effect results in photographs of the body in which the veins stand out as dark prominent lines against a light background as illustrated by comparing the arm shown in FIG. 1A irradiated with normal light to the same arm shown in FIG. 1A irradiated with infrared.
Various components including mirrors and filters for infrared radiation have been disclosed.
For example, U.S. Pat. No. 5,233,465 to Wheatley et al discloses a polymeric multilayered film which reflects wavelengths of light in the infrared while being substantially transparent to wavelengths in the visible spectrum. The wavelength is selected by appropriate selection of the "optical thickness" of the multilayers defined as the physical thickness multiplied by the index of refraction.
U.S. Pat. No. 3,514,174 to Gans discloses a multilayer interference transmittance filter for use in the infrared region of the spectrum.
Filters and mirrors operating at selective wavelengths can be custom made and purchased from the Rolyn Optics Co., Covina, Calif.
Devices have been developed which intensify images formed by infrared radiation. These image intensifiers are incorporated into "night vision goggles" disclosed in the patent literature.
For example, U.S. Pat. No. 5,248,874 to Raverdy discloses an image intensifier tube having a connected brightness curve.
U.S. Pat. No. 5,204,774 to Owen et al discloses a night vision goggle with an achromatic lens assembly.
"Liquid Crystals, Applications and Uses" by Birendra Bahadur, vol. 1, chapter 16, 1990, published by World Scientific, discloses construction of image intensifiers. FIG. 4 is a sectional view of an image intensifier of the prior an showing the incident image on cover 52, transparent conductive electrodes 54, photoconductor 56, light block 58, dielectric rain or 60, liquid crystal alignment films 62, liquid crystal 64, cover 52.
None of the cited art discloses or suggests the adaptation of these technologies to the act of gaining intravenous access fox the purpose of eliminating the trauma associated with locating a suitable vein.